Some ESX 4.x and ESXi 4.x network settings stored in /etc/sysconfig/network are migrated in the upgrade or migration to ESXi 5.x. In the migration to ESXi 5.x, ESX Service Console virtual NICs (vswifs) are converted to ESXi virtual NICs (vmks).
The distributed port group or dvPort that the virtual NICs connect to is also migrated. The Service Console port group is renamed as the Management Network port group. When vswifs are migrated to vmks, they are numbered to follow any existing vmk in sequence. For example, if the version 4.x ESX host has virtual NICs vmk0, vmk1, and vswif0, after the migration the new ESXi configuration will be vmk0, vmk1, and vmk2, where vmk2 is the management interface.
When virtual NICs are configured to use DHCP, a setting controls whether DHCP sets the default route and host name in addition to installing an IPv4 address. In ESX this setting is PEERDNS. In ESXi, the setting is DhcpDNS. The PEERDNS value for ESX Service Console virtual NICs is migrated to the DhcpDNS setting for the ESXi virtual NICs. The DhcpDNS setting preserves the ESX configuration for default route and host name as well as the IPv4 address.
The migration from ESX 4.x to ESXi 5.x also preserves manually assigned IPv4 and IPv6 addresses, default route, and host-specific IPv4 and IPv6 routes.
When you upgrade from ESXi 4.x to ESXi 5.x, the default maximum number of ports for a virtual switch changes from 64 to 128. To keep the same maximum number of ports that you have in ESXi 4.x, set the value explicitly before you upgrade, using the vSphere Web Client.
ESX hosts have two IP stacks, one for the vmkernel and one for the Service Console. Because ESXi hosts have only one IP stack, the migration cannot preserve both ESX default routes. After migration, the ESX Service Console default route becomes the single ESXi default route, replacing the vmkernel route. The change to a single ESXi default route might cause loss of connectivity for routed nonmanagement traffic that originates from vmkernel. To restore vmkernel networking, you can configure static routes in addition to the default route.
All vswif interfaces are migrated to vmk interfaces. If a conflict is detected between two interfaces, one is left in disabled state. The upgrade disables any conflicting kernel IP addressing in favor of the management interface.
The migration to ESXi 5.x disables any existing vmk virtual NIC that meets the following conditions.
The vmk virtual NIC has a manually configured (static) IP address.
The IP address is in the same subnet as a vswif virtual NIC that is being migrated to a switch containing the vmk virtual NIC.
The vmk and vswif NICs are both on the same virtual switch.
For example, if vswif0, with IP address 192.0.2.1/24 on vswitch1, is migrated to a switch containing vmk0, with IP address 192.0.2.2/24, also on vswitch1, after the migration, vmk0 will be disabled.